Exterior ducts for transfer of air between an interior location within a building and an air management system exterior to the building, the duct typically comprise a metal duct wall defining a hollow interior through which the air passes between the interior location and the air management system with at least part of the metal duct wall exterior to the building and thus subject to the exterior environment. In order to reduce heat loss a layer of rigid insulation material surrounds at least the exterior part of the metal duct wall. This is particularly important in locations where extreme temperature differences are possible but is advantageous everwhere.
Existing alternatives for covering and protecting the insulation material are as follows.
A layer of glass fiber and mastic (tar) is applied. This is a very old technique for outdoor ventilation insulation protection. Insulation is applied, followed by a layer of mastic (tar) troweled on to the insulation, followed by a glass fiber mesh applied/embedded to the mastic followed by a final layer trowel coat of mastic. This application is still being used to date. It is plagued with leaks from the date of installation, and has no ultraviolet/ozone resistance. It is a very messy application with a very unappealing appearance.
An aluminum Jacket is applied. This is another very old technique for outdoor ventilation insulation protection. Insulation is applied, then an aluminum or stainless steel clad finish is applied over the insulation. Years ago the cladding would be bent and manipulated to fit with sheet metal equipment onsite. Each piece of cladding would then be joined together with screws or rivets and sealed with a bead of silicone caulking.
Over the years the fabrication equipment is no longer onsite and now the cladding is being applied flat to all the 4 sides and affixed to the insulation with foil tape. The four sides (corners) of the cladded ducting now has matching corner beading applied and fastened with screws all around, followed by a bead of silicone caulking applied to all the joints. The joints break open over time causing leaks, the screw holes are never sealed causing seepage of water from the date of installation. The aluminum also dents from maintenance workers and hail.
This is the last alternative is sold under the trademark Ventureclad. This is essentially a 2 feet wide roll of foil self-adhesive tape. It is a peel & stick application. This product is made to look like the aluminum jacket. Companies often quote aluminum but on site substitute this product because the appearance is somewhat the same. This product is supposed to be applied with an overlap and simply rubbing it down with a plastic applicator supplied with the product. Because of the little holes that would be visible on the top side of the ventilation ducts from the edges unsticking over time. The mechanical insulators would simply apply a bead of aluminum (silver) caulking to all the joints. The manufacturer does not ask for this to be done. The trade's people do it to minimize call backs.
The other problems with this product is that birds (crows/ravens) will peck holes threw the product. It also shows hail damage easily and can be damaged by maintenance workers. Also because the duct installers seldom seal the ventilation ducts 100%, the leaking air from the duct acts to create a ballooning effect on the product which looks totally unsightly and causes it to pull away from the insulation layer underneath.